JDK-8214753 : (opt) add Optional::transform, allowing an arbitrary operation on an Optional
  • Type: Enhancement
  • Component: core-libs
  • Sub-Component: java.util
  • Priority: P4
  • Status: Open
  • Resolution: Unresolved
  • Submitted: 2018-12-04
  • Updated: 2024-05-10
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tbdUnresolved
Related Reports
Relates :  
JDK-8203442 - String::transform
Relates :  
JDK-8331875 - Enhance the utility of java.util.Optional with additional lambdas
Description
Add a method something like this to Optional:

    public <R> R transform(Function<Optional<T>, ? extends R> f) {
        return f.apply(this);
    }

This allows the caller to provide an arbitrary operation to be performed on "this" Optional, regardless of whether it's empty or present. The name "transform" follows precedent set by String::transform (JDK-8203442).
Comments
Applying the PECS or get/put rule would seem to indicate that the signature should be <R> R transform(Function<Optional<? super T>, ? extends R> f) but this doesn't actually have the desired effect of allowing a function that accepts a supertype of Optional<T>. Suggestions welcome.
04-12-2018